This invention relates to a composition and process useful for cleaning aluminum-containing articles. More particularly, the invention relates to a composition and process for removing debris, e.g., smut, unwanted deposit material, soil and the like, from such articles, e.g., aluminum foodstuff or beverage containers or cans.
Aluminum-containing articles are often formed into shapes using lubricants to assist in the forming process. For example, one or more lubricants are often employed in the drawing and ironing of aluminum container bodies of the type used to package foodstuffs and beverages. The forming processing itself and/or the lubricant or lubricants employed produce debris, e.g., as noted above, on the article which interferes with the over-all appearance of the article. In certain instances, this debris is referred to as smut. In general, such smut or smut-like material includes aluminum and/or alumina fines and/or lubricant material and/or lubricant residue. Such debris should be removed to provide an aluminum-containing article which is visually pleasing and, more importantly, make the article suitable for use, e.g., as a foodstuff or beverage container.
Various compositions have been suggested for use in cleaning aluminum articles. For example, King, et al U.S. Pat. No. 4,599,116 discloses an aqueous alkaline (a pH of at least 10) cleaning composition containing an alkalinity agent present in an amount to achieve removal of aluminum fines, a complexing agent, and one or more surfactants. Preferred alkalinity agents include alkali metal hydroxides and alkali metal carbonates. Among the complexing agents are gluconic acid, citric acid, glucoheptonic acid, sodium triphosphate, EDTA, tartaric acid or the like, as well as the soluble and compatible salts thereof and mixtures thereof. The relatively strong alkalinity agents employed could harm, e.g., etch, the aluminum surface unless care was exercised to control the cleaning operation.
Dollman U.S. Pat. No. 4,370,173 discloses removing lubricating oils and aluminum fines from aluminum surfaces using an aqueous solution of sulfuric and hydrofluoric acids and an anionic surfactant. Michelson, et al U.S. Pat. No. 3,448,055 discloses removing smut from aluminum with an aqueous composition including nitric acid, sulfuric acid, hydrofluoric acid, phosphoric acid and a surfactant. Such solutions of strong acids are effective to clean the aluminum 15 surfaces, but also tend to etch the surface as well. Such etching is undesirable.
Earhart U.S. Pat. No. 4,713,119 discloses removing alkali metal aluminum silicate deposits from chemical processing equipment by alternating treatments with acidic and basic solutions. The acidic solution contains sulfuric acid, sodium bisulfate, tartaric acid or phosphoric acid. This patent does not disclose cleaning aluminum-containing surfaces nor that the acidic solution includes a surfactant.
Wood, et al U.S. Pat. No. 4,264,418 discloses removing oxide film from metals or alloys containing iron, nickel, copper, beryllium, chromium, gold, zinc, lead, or tin with a composition containing gluconic acid or its alkali metal salts, citric acid or its alkali metal salts, or tartaric acid or its alkali metal salts and, preferably, a non-ionic surfactant. Aluminum-containing articles are not disclosed. Further, no "strong" acid is included in the composition.
Laporte, et al U.S. Pat. No. 3,306,773 discloses treating sintered aluminum parts with an aqueous alkaline solution before putting such parts into heat transfer surface. Pikaar U.S. Pat. No. 3,211,659 discloses acids, such as acetic acid, EDTA, citric acid, tartaric acid, gluconic acid, glyceric acid, malic acid, glycolic acid, saccharic acid, phosphoric acid, and benzoic acid for cleaning egg shells. Vinso U.S. Pat. No. 3,527,609 discloses the use of tartaric acid salts among salts of many polycarboxylic acids for use in cleaning cooling water systems. Rubin U.S. Pat. Nos. 4,049,467 and 4,129,423 disclose removing manganese derived discolorations from hard surfaces by use of either dihydroxy maleic acid, dihydroxy tartaric acid, their alkali metal salts, or mixtures thereof. None of these references is concerned with relatively heavy duty cleaning of, e.g, smut removal from, aluminum surfaces.
Yamasoe et al U.S. Pat. No. 4,728,456 discloses an aluminum surface cleaner which is an aqueous highly acidic solution containing sulfuric acid and/or nitric acid, ferric ions, but no chromium or fluoride ions. Yamasoe et al discloses that the etching of the aluminum by the sulfuric acid or nitric acid is promoted by the ferric ions. Also, Yamasoe et al discloses that chelating agents, such as citric acid and tartaric acid, can be included to accelerate the aluminum etching rate.